The lactoperoxidase system: the influence of iodide and the chemical and antimicrobial stability over the period of about 18 months

Abstract

The lactoperoxidase (LP) system is a natural antimicrobial system, the use of which has been suggested as a preservative in foods and pharmaceuticals. The effect of adding iodide to the LP system, the chemical stability and the change in antimicrobial effectiveness during storage was studied. Addition of iodide with thiocyanate increased the fungicidal and bactericidal effect against Candida albicans, Escherichia coli and Staphylococcus aureus. Pseudomonas aeruginosa showed the same inhibition in the LP system with iodide and without iodide. Storage of the LP system in completely filled airtight containers for 18 months caused a 35% loss of the initial thiocyanate concentration. The antimicrobial activity of this LP system was strong enough to kill inocula of 106 cfu ml−1 of the four test organisms within 2 h of contact time. During storage of the air‐containing LP system, the concentration of thiocyanate was reduced below detection limit within 7 d, the concentrations of hypothiocyanite and hypoiodite within 350 d. After 516 d the antimicrobial activity of air‐containing LP system was strong enough to kill inocula of 106 cfu ml−1Ps. aeruginosa within 2 h, Staph. aureus within 4 h and Candida albicans and E. coli within 1 week of contact time.

In-Vitro Inhibition of Pythium ultimum, Fusarium graminearum, and Rhizoctonia solani by a Stabilized Lactoperoxidase System alone and in Combination with Synthetic Fungicides

“…Bosch et al demonstrated that LPO at a concentration of 387 nM in an LPO system similar to the one used here was sufficient to kill 1,000,000 CFU of C. albicans, E. coli, Staphylococcus aureus, and P. aeruginosa when exposed to the LPO system in solution for at least two hours [27]. We found that a slightly lower concentration of LPO (323 nM) was sufficient to inhibit, but not kill, the fungi R. solani and F. graminearum, and a much lower concentration (20 nM) was sufficient to completely kill the oomycete P. ultimum.…”

“…We found that a slightly lower concentration of LPO (323 nM) was sufficient to inhibit, but not kill, the fungi R. solani and F. graminearum, and a much lower concentration (20 nM) was sufficient to completely kill the oomycete P. ultimum. Although the LPO concentrations that were used in the Bosch et al study were relatively similar to the highest LPO concentration that was included in this study, the assay conditions were very different [27]. The majority of studies on the antimicrobial activity of the LPO system conducted to date, including the Bosch et al study, have involved bacteria and yeasts that were exposed to a non-stabilized LPO system in a liquid suspension [27].…”

“…Pythium ultimum was more sensitive to the LPO system than F. graminearum and R. solani, requiring approximately 30 times less enzyme to achieve comparable levels of inhibition. The difference in sensitivity between fungi and oomycetes was not surprising, given that different organisms are known to vary in their sensitivity to the LPO system [27]. To date, most of the studies involving the LPO system have focused on human bacterial pathogens, such as Staphylococcus spp., Pseudomonas aeruginosa, Escherichia coli, Streptococcus spp., and yeast like Candida albicans [27][28][29].…”

“…The difference in sensitivity between fungi and oomycetes was not surprising, given that different organisms are known to vary in their sensitivity to the LPO system [27]. To date, most of the studies involving the LPO system have focused on human bacterial pathogens, such as Staphylococcus spp., Pseudomonas aeruginosa, Escherichia coli, Streptococcus spp., and yeast like Candida albicans [27][28][29]. A few studies have demonstrated activity against spores of filamentous fungi, such as Aspergillus fumigatus, Aspergillus niger, Mucor rouxii, and Byssochlamys fulva [30,31].…”

Candida Biofilms on Oral Biomaterials

“…Other investigations demonstrated 1) that lactoperoxidase activity was not modified by coating onto titanium, 2) that lactoperoxidase incorporated in oral gel maintained its activity for at least one year, and 3) that the substrate exhaust (namely hydrogen peroxide and iodide) was the true limiting factor (Bosch et al, 2000;Ahariz et al, 2000). Previous investigations indicated an antibacterial effect on Gram-positive and Gram-negative bacteria, which suggests a non-specific inhibitory effect of hypoiodite on microbial metabolism and growth (Courtois et al, 1995).…”